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10 Gases Solutions to Exercises 10.110 (a) Pressure percent = mol percent. Change pressure/mol percents to mol fraction. Partial pressure of each gas is mol fraction (x) times total pressure. Px = = 0.748(0.985 atm) = 0.737 atm; = 0.153(0.985 atm) = 0.151 atm Pco₂ = 0.037(0.985 atm) = 0.03645 = 0.036 atm PH₂O = 0.062(0.985 atm) = 0.06107 = 0.061 atm (b) PV = nRT, n = PV/RT; P = 0.036 atm, V = 0.455 L, T = 37°C = 310 K n = 0.03645 atm X 0.455 310 K L 0.08206 mol K atm = 6.520 X 10⁻⁴ = 6.5 X 10⁻⁴ mol - (c) 1 10.111 V and T are the same for He and / = RT/V; nHe = = ; nHe = 1.42 He 4.003 1 mol g He He = 0.3547 = 0.355 mol = 42.5 158 torr 0.355 mol = 1.3188 = 1.32 mol O₂; 1.3188 mol O₂ 32.00 1mol O₂ = 42.2g O₂ 10.112 0.08206 mol- K atm 355 400 torr K X 760 1 atm torr = 77.579 = 77.6 g/mol = mole fraction O₂; = mole fraction Kr 77.579 g = x(32.00) + x)(83.80) 6.22 =51.80 = 0.120; 12.0% O₂ 10.113 (a) The quantity d/P = MM/RT should be a constant at all pressures for an ideal gas. It is not, however, because of nonideal behavior. If we graph d/P vs P, the ratio should approach ideal behavior at low P. At P = 0, d/P = 2.2525. Using this value in the formula MM = d/P RT, MM = 50.46 g/mol. 2.32 2.31 2.30 d/P 2.29 2.28 2.27 2.26 0.2 0.4 0.6 0.8 1.0 1.2 P (atm) (b) The ratio d/P varies with pressure because of the finite volumes of gas molecules and attractive intermolecular forces. 300